April 21, 2006 | General

Closing The Loop On Anaerobic Digestion

BioCycle April 2006, Vol. 47, No. 4, p. 66
Developed at Rutgers University with Bioscan, a Danish firm, the technology separates organics into usable components. A 10 megawatt facility is being constructed in Belmont, Wisconsin.
Cindy Rovins

ORGANIC ENERGETICS is an environmentally closed looped, self-sustaining waste to energy process developed at Rutgers University and marketed by Bioscan A/S, Denmark and U.S. The system uses a series of processes to degrade products into their primary components: anaerobic digestion, membrane filtration, reverse osmosis, gasification, and membrane gas separation. The patent pending technology was developed by Dr. Paula Marie Ward, Assistant Research Professor in the Department of Biochemistry and Microbiology at Rutgers University’s Cook College.
Ward’s Ph.D. is in Animal Sciences and she teaches and researches antibiotic resistance in food and water systems. It was through her interest in disabling antibiotics entering the environment from animal wastes that she developed the organic energetics process. Antibiotics are used as growth promotants in animals. When agricultural pesticides, hormones and antibiotics from plants and animals get into the surface water, the biological impact of those residues can create antibiotic-resistant organisms. When exposed to humans, animals and plants, these antibiotic-resistant organisms can create diseases that are very difficult or impossible to suppress.
As a researcher studying the land application of animal waste and its microbiology and looking at where resistant organisms could come from in surface water and soils, she realized the amount of antibiotics we use to raise animals in this country could contribute greatly. “According to the Union of Concerned Scientists, approximately 70 percent of the pharmaceuticals we produce in this country are used to increase the growth rate of animals, with less than 30 percent used for humans and the rest for plants,” says Ward. “With that kind of number and the way we handle animal waste, it is evident where some of the resistance could be coming from, and that is why I wanted to stop it – it is something we can control. If we are not going to stop using the antibiotics, then let’s at least contain them.”
Creating the system mainly as a solution for lagooned animal waste in Concentrated Animal Feeding Operations (CAFOs), Ward was introduced to Bioscan of Denmark, a company with a patented state-of-the-art anaerobic digestion system that met her criteria in terms of an environmentally closed-loop operation.
Denmark requires concrete lagoons to prevent fugitive seepages. However, after noticing that land application of the digestate was excessive – the ratios of available nutrients to what was required for plant uptake were too high – Denmark put restrictions on land application. Bioscan looked at mechanically converting animal waste via containerized anaerobic digestion into products that can be harvested and reused. Its patented Biorek process uses several digestion and separation technologies which result in a cleaned up methane/CO2 stream, the harvesting of ammonia, the stripping of potassium and phosphorus salts from the liquid digestate, and purification to provide potable water. The cleaned methane can be used for energy and the salts can be land applied in proportions that plants can use. They are also left with a solid “compost”.
Although the Biorek technology had highly refined the anaerobic digestion process, it still could not disable the U.S. pharmaceutical products, either in whole or their metabolites, which sometimes can be as effective as the original drug. Ward collaborated with Bioscan and added another technology to its AD system – gasification, which would take the solids from the digestate and crack the hydrocarbons, but not destroy them, so that producer gases can be harvested. The producer gases can be reformed into Syngas and other beneficial uses. The gasifier phase also results in an ash product, which contains the remaining carbon and trace metals including potassium and phosphorus. And most importantly for Ward, along with adsorbents used to filter pharmaceuticals from the liquid phase, the higher temperature of gasification in comparison with anaerobic digestion disables the pharmaceuticals in the solid residual.
The gasification phase also achieved another one of Ward’s goals – to completely close the loop on anaerobic digestion. While deriving energy, purified gases, salts and water from the Biorek process, a solid compost is an additional end product. Through gasification, the components are further separated, so that all by-products of the system are useful, marketable products.
“We need not look farther than ordinary, everyday organic materials for production of the thermal and mechanical power we have come to expect to accommodate our daily lives,” explains Ward. “Viewing waste resources as valuable could start directing society to understand the value of the two-way transformation of organic matter into and out of free, gaseous energy. Power generation from subterrestrial organic fuel sources such as oil, natural gas, and coal is essentially no different from surface forms, providing that the mechanical technologies exist to complete the transformation. In addition, products manufactured from subterrestrial energy sources can also be synthesized from the breakdown products of surface organic sources.”
How best to mine our wastes for valuable resources? Ward shares the philosophy that she, along with other key players in New Jersey and elsewhere are working to implement. “It’s more about a philosophy of integrating a wider variety of technologies that are appropriate to a region or facility or a feedstock stream that makes better use of what has been previously considered waste and turn it back into useful products, including energy and clean water. This big picture thinking is where we need to go in handling our waste.” Ward adds one caveat to this theory: “The focus is not about the renewable energy that can be derived from conversion, but rather how we need to be smarter about how we sustainably handle and terminate our ever-increasing waste stream.” (See sidebar on Integrated Waste Technologies.)
In addition to animal waste processing, the Organic Energetics technology can be applied to wastewater processing, grease trap wastes, organic industrial wastes, food processing plants or colocated with landfills. By using an anaerobic digester with a gasifier, presorted commercial and household food waste, and nonrecyclable paper, plastics and packaging can be converted into usable fuel. The gasifier can further harvest residual power out of plastics that can’t be degraded in the digester. Down the road, colocating a digester and gasifier next to landfills also lends itself to the mining of old, dead capped landfills.
A key factor for sewage treatment plants is an issue not yet on the public health and environmental sector’s radar screen – pharmaceutical products in the human waste stream. Just like the presence of pharmaceuticals in animal waste, in human sewage sludge, the pharmaceuticals end up in the biosolids. Explains Ward, “Many drug compounds go right through human and animal systems, virtually unchanged.” Anticipating that these will be the next compounds to be regulated in wastewater treatment effluent, Ward emphasizes that there are patented ways to treat them: different kinds of filtration systems disable and filter the compounds from aqueous systems, and high temperatures from processes such as gasification disables them in the solids.
Another innovative application of this technology is for residential housing. Economy of scale predicates using the system in a cluster facility, rather than an individual home. Residential systems would entail pumping and piping. They can use the products themselves, water and biogas for heat and electricity, and depending if they have land, they can use the trace nutrients as fertilizers. The system can be applied to new construction, or retrofitted to existing construction. The exterior of a neighborhood conversion facility can look architecturally like a house, so it doesn’t detract from the aesthetics of the neighborhood.
Under consideration for U.S. military use, the Organic Energetics system is seen as a production source for key materials as well as a solution for disposal problems. The production of water, fuel, hydrogen and other viable products such as ammonia, phosphorus and potassium entails a cost savings on purchasing and shipping from outside sources. Cost avoidance also results from reduced and eliminated transportation for waste disposal.
Table 1 lists wastes that are suitable to be processed using the Organic Energetics technology. Materials that are not suitable include aluminum, and halogenated products such as polyvinyl chloride, chlorine, fluorine and bromine. These pose a disposal issue and require separation. End products from the Organic Energetics processes include: Anaerobic Digestion Phase: Ammonia, biogas (methane), CO2, sulfur; Liquid/Solid Separator Phase: Potable water, potassium and phosphorus salts; Gasifier Phase (depending on feedstock profile): Hydrogen, carbon monoxide, CO2, nitrogen, ash, and traces of water, ammonia, methane, ethane, ethane and hydrogen sulfide gas.
The Biorek facilities already in operation span the globe. Projects in Denmark, Germany, Japan, Australia and Holland all deal with animal waste feedstocks. A facility being built in Canada will handle the distiller’s grains in an old whiskey plant to produce ethanol. Another plant is planned for Denmark, which will take a mix of industrial organics, including fish and slaughterhouse wastes.
Says Poul Ejner Rasmussen, Bioscan’s Director of Business Development: “We started with animal wastes because that was the biggest volume problem in Europe.” The current Denmark plant is a 2 megawatt facility that processes 600 metric tons/day of organic feedstock.
The first facility to implement the Organic Energetics technology will be Belmont BioAg, in Belmont, Wisconsin. A fluidized bed reactor will be used to produce steam. Belmont BioAg is an environmentally inspired agricultural campus design integrating various processes. “Their main purpose is to produce ethanol, but they’ve colocated their site at an access point for corn for ethanol as feedstock, as well as CAFO or feedlot waste so they can take the animal waste as well as the ethanol production waste,” says Ward. “The various liquors and grain wastes from the ethanol process go into a digester to produce power to heat and run the ethanol plant. They are also moving spent heat to greenhouses.” Bioscan’s Biorek system will be used as the anaerobic digester and will be a 10 megawatt facility. The Belmont project, which is in the development stage, can be read about at http:// www.belmontbioag.com/.
Cindy Rovins is an Agricultural Communications Editor for Rutgers Cooperative Research & Extension.
GASIFICATION is a technology that has been widely used in commercial applications in the production of fuels and chemicals for over 50 years. The process converts materials having carbon and hydrogen into clean synthesis gas, or Syngas, a mixture of hydrogen and carbon monoxide. Syngas can be used as a fuel to generate electricity or steam, or as a basic chemical building block for the manufacturing of commercial chemicals. Hydrogen can also be extracted from the process and used in fuel cells.
According to the California Integrated Waste Management Board, “Typical raw materials used in gasification are coal, petroleum-based materials and organic materials. The feedstock is prepared and fed in dry form into a sealed reactor chamber called a gasifier. The feedstock is subjected to high heat, pressure and either an oxygen-rich or oxygen-starved environment within the gasifier. Most commercial gasification technologies do not use oxygen.”
There are a variety of gasifiers that can be used in the Organic Energetics system to process waste to energy. These include downdraft gasifiers, fixed bed or fluidized bed gasifiers, but according to Dr. Paula Marie Ward, the selection would depend on the feedstock put into the system, and what products you want to get out.
Gasification has many advantages over incineration of solid waste from an emissions standpoint. In a mass burn incinerator, combustion rapidly takes place in a single chamber. In addition to carbon, hydrogen and oxygen, biomasses contain additional chemicals. In combination with air, which is comprised of oxygen and nitrogen, competing reactions take place that produce environmental contaminants. For example, at high temperatures, nitrogen from the air can combine with oxygen to form oxides of nitrogen (NOx). Sulphur combines with oxygen to produce oxides of sulphur (SOx). Chlorine and unburned hydrocarbons can create dioxins, furans, and other toxic chlorinated organic compounds. Additional contaminants from the high temperature reactions of unsorted municipal solid waste can produce vaporized mercury or lead, hydrocarbon gases or carbon monoxide, as well as soot and particulate matter. To regulate the amount of these pollutants released into the atmosphere, various air pollution control devices are used on incinerators.
A drawback to incineration of unsorted municipal waste is the potential contamination of heavy metals. However, if the presorting factor is taken out of the mix and presorted waste incineration is compared to presorted waste gasification, gasification would still come out ahead emissions-wise. Because gasification uses much lower temperatures than incineration, the critical temperature for oxidizing the metals does not occur. Even if the gasification process uses oxygen, the oxygen is self-consumed and reforms within the feedstock conversion. With lower temperatures, most of the potentially harmful air pollutants remain in the discharged solid ash. The remnant ash can be used as low density aggregate fillers such as fertilizer trace metals, ceramics, and in cement manufacturing.
The key to having a pure efficient gasification process is the separation and sorting of the municipal solid waste stream. Either separated at the source or in a Materials Recovery Facility, the recyclable materials and potentially hazardous materials are segregated from the waste stream.
Gasification lends itself well to plastic materials. For nonrecyclable plastics, except polyvinyl chloride, gasification has been proven an efficient technology, already implemented in several countries including Japan, Canada, Spain and Finland. Plastics are ideal for the gasification process because of their high calorific values and are made up primarily of hydrogen and carbon.
PART of Dr. Paula Marie Ward’s time is spent at the Rutgers EcoComplex, the off-campus research station located at the Burlington County Resource Recovery Complex in New Jersey, where she works on renewable energy technology business development. From there, she has been involved in several integrated waste technology initiatives. “Integrated technology sites, in terms of business development and creation of jobs and industry, have a good economic model involved here,” explains Ward. “You’re getting tipping fees for the resources you’re putting into the system and getting paid for the products you’re getting out of the system. That’s a positive economic model that the investment community is beginning to recognize. If you can get long-term contracts for your feedstock and products – whether renewable energy or fertilizer, that is what gets you your funding. Investors are looking for the return on the investment. Also, if the technologies are proven, the permitting is easier to get.”
Landfills, transfer stations and wastewater treatment sites are logical homes for integrated conversion technologies. For example, putting not just a digester at a landfill, but an array of technologies makes sense for the feedstock stream.
Ward cites other potential uses for integrated technologies. Wastewater treatment plants that are doing anaerobic digestion and harvesting methane, but flaring off what they can’t burn in a cogeneration facility, can consider turning it into liquid fuel using scrubbing technologies to clean up the gas. These facilities, she claims, for a state like New Jersey with its clean energy initiative, can be the lead guard in the war on getting renewable energy produced in the state. “They already have the infrastructure, facilities, the soluble organic waste influx, and the water supply coming through. So, if the New Jersey Board of Public Utilities wants to see more renewables coming into use in the state, they don’t have to go far to get the production started; they just have to enable their wastewater treatment facilities.”
Another advocate of integrating waste technologies is Robert Simkins, Director of the Burlington County Resource Recovery Complex, where the EcoComplex is located. The Burlington County site is a prime example of how various technologies can interface, with landfill gas (LFG) used both to heat an aquaponics greenhouse and to fuel trash trucks in addition to other synergistic systems colocated at the landfill (see BioCycle, December 2004). Simkins cites an integrated initiative in Ohio in the works that was spawned from the initial work done at Burlington County from the technology to clean up the LFG. “This will be their first commercial sized facility,” says Simkins. “It will be a showcase that will move this along in a quantum leap.” The initiative will be at the Solid Waste Authority of Central Ohio (SWACO), one of the largest public sector landfills in the U.S., including a transfer station.
Tim Berlekamp, SWACO’s Director of Planning and Business Development, explains that they will be working with Firm Green of Newport Beach, California to develop a “Green Energy Center”. Firm Green bought the proprietary technology of Acrion Technologies, Inc.’s LFG clean-up system, which was piloted at Burlington County. “SWACO will sell its LFG to Firm Green Fuels (an LLC of Firm Green Energy) who will clean the gas through the proprietary Acrion process,” says Berlekamp. “The cleaned gas will then go through either fuel cells and/or microturbines to produce electricity for both Firm Green Fuels and SWACO’s designated facilities. The second phase – to produce compressed natural gas, which we will test and, subject to successful results, will convert our transfer fleet to dual fuel vehicles. Our trucks would run on compressed natural gas and biodiesel.”
The final stage of SWACO’s plan is to utilize Acrion’s complete process to produce methanol and food grade carbon dioxide. They are also looking at a hydrogen stream for experimentation with fuel cells from the production of methanol. And, last but not least, they are in the process of promoting and funding a green industry business park with an incubator. The green energy from the fuel center will provide the energy for the business park, and the buildings will be built to LEED standards (Leadership in Energy and Environmental Design) of the U.S. Green Building Council.
Says Berlekamp, “We’d like to become the second generation of the EcoComplex – going from a laboratory one to a commercial grade one. Just like they started with this process, we’re going to expand it into more infrastructure.”
Berlekamp explains the paradigm shift that Ohio, a rust belt state in the auto and steel industries, is undergoing. “We asked, how do we make landfills a part of an economic development engine? There’s feedstock there, there’s energy, there are a lot of things that we just haven’t tapped. So that’s the vision that put this all together.”

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